YS Versioning
YS is a "versioned" programming language.
It uses the Semantic Versioning 
scheme.
Major compatibility breaking changes are allowed between major versions.
All programs and data files that use YS code expressions must declare the major version of YS they use.
The current major version is 0, which means that the language is still under
development.
That said, the language has been fairly stable for a while now.
Very soon we will declare v0 stable and start working on v1. Soon after that, v1 will be declared stable and we'll start working on v2. The v1 "development" period is just a practice run for switching major versions. v1 stable should be nearly identical to v0 stable.
In fact, we plan to deprecate v0 after v1 is stable. After a couple months of v0 deprecation, use of v0 will be disallowed.
The v2 "development" period will be a much longer period.
The stable v2 runtime will support both v1 and v2 programs and libraries.
See YS v1 Planning for a description of the changes we need to make to release YS v0 as a stable YS v1, and then start working on YS v2.
Rules for Version Usage🔗
YS programs must declare their major version.
They usually do this with a stream tag like !YS/v1.
They can also use a shebang line to declare the version:
#!/usr/bin/env ys-1
You need the -1 part or !YS/v1 won't be added.
Alternatively, you could do this:
#!/usr/bin/env ys
!YS/v1
-e Versioning
When using the -e flag, the expression is assumed to be code mode and an
explicit !YS/v1 tag is not needed.
This is for simplicity of 1-liners.
The version is determined by the major version of the ys binary being
used.
Rules for New Version Development🔗
Work on v2 might last a year. During that time, we will be putting out new v1 releases.
We will also be putting out new v2 alpha releases on a regular basis.
We want to let people start using v2 as soon as possible.
This requires that we have a v2 versioning scheme in place and syntax rules for using v2.
These rules should be compatible with semver rules.
Current v0 Binary Naming🔗
<prefix>/bin/ys(symlink)<prefix>/bin/ys-0(symlink)<prefix>/bin/ys-0.1.97<prefix>/lib/libys.so-0.1.97
New v1 Naming🔗
<prefix>/bin/ys(symlink)<prefix>/bin/ys1(symlink)<prefix>/bin/ys-v1(symlink)<prefix>/bin/ys-1.2.3<prefix>/lib/libys.so-1
When v1 is final stable, we just need to match the major version.
New v2 Naming🔗
For the time where v1 is final stable and v2 is in development:
During development, the version will always start with 2.0.0.
Then we'll have a -alpha suffix followed by a minor and patch version.
When alpha-minor is zero, then any change can happen.
This is like a normal major version of 0.
So we start at 2.0.0-alpha.0.1.
This is similar to a 2.0.1 version that is alpha (mentally removing the
.0.0-alpha. part).
When we go to 2.0.0-alpha.1.1, we've come to a point where things are
stabilizing and we want to indicate a breaking change by bumping the alpha-minor
number.
This scheme is compatible with semver and ensures ever-increasing versions.
New v2 Binary Naming🔗
<prefix>/bin/ys(symlink)<prefix>/bin/ys2-a(symlink)<prefix>/bin/ys-v2-a(symlink)<prefix>/bin/ys-2.0.0-alpha.0.1<prefix>/lib/libys.so-2.0.0-alpha.0.1
v2 Shebangs🔗
To use a shebang for v2 while it is still in development:
#!/usr/bin/env ys-2-a